It is necessary to examine whether micron-sized grains
can be ejected from the Solar System, because such small grains are
affected by non-gravitational processes in interplanetary space,
in contrast to larger bodies [1]}, [2]}.
The collisional disruption time is shorter than \(10^{6-7}\)  yrs for grains smaller than 1 cm
[3]}, and they are converted into smaller grains during the
typical residence time in interplanetary space.
Magnetic fields are not important for grains larger than 1 \(\mu \) m,
but the Poynting-Robertson (PR) drag time is
shorter than the collisional time for grains smaller than 100 \(\mu \) m.
Then these particles will spiral into the Sun within \(10^6\)  yrs, but
collisions are still effective to produce even smaller micron-sized grains.
Solar radiative pressure is greater compared to gravity for smaller grains,
and the two forces are comparable at \(\sim 1 \ \mu \) m
size. These grains are then ejected from the Solar System as “beta meteoroids”
[4]}, [1]}, and consequently
a significant fraction of originally 1–\(10^4 \ \mu \) m ejecta will eventually escape
from the Solar System as micron-sized grains [3]}, [7]}, [8]}.
In the following, it is assumed that
the Solar System is typical among planetary systems in the Milky Way,
and grains about \(1 \ \mu \) m in diameter (\(m \sim 10^{-12}\)  g
for a spherical grain of density \(\sim 3 \ \rm g \ cm^{-3}\) )
that were originally on a planet's surface are ejected from a planetary system
into interstellar medium (ISM) at a rate of \(\dot{M}_{\rm ej} = 10^4\)  kg/yr.
